The proposed research involves a study of lens regeneration from the iris, neural retina regeneration from the pigmented, retinal epithelium and the reconstitution of a lens from lens epithelium in urodele amphibians. It is hoped to obtain information concerning the stimuli which release the metaplasia occurring and the role of trophic factors during regeneration. Synthesis of macromolecules and cytological changes in the reacting tissues will also be studied. Some of the aspects to be investigated are the ultrastructural and synthetic events taking place in lens capsule formation during lens regeneration in adult newts, ultrastructural changes during dedifferentiation of the iris and beginning lens differentiation in young and old larvae, releasing mechanisms for neural retina regeneration and the pattern of uptake of tritiated uridine and amino acids during this process, and studies of recycling, if any, of tritiated thymidine in adult newts. DNA synthesis, cell proliferation and growth rates in embryonic lens vesicles developing in ocular and extra-ocular sites in larval hosts and possible similarities between the actions of the lens inductor from the embryonic eyecup and the neural retinal trophic factor in lens regeneration will also be examined.